For vacuum cleaners, the state of the art is a conventional workshop vacuum, which is a sealed canister with a lid. The vacuum suction is provided by a vacuum motor unit, usually mounted through the lid. A foam filter sleeve is typically included on the suction inlet, around which there may be disposed a bag or filter element. Such workshop vacuums typically use a “Clean Impeller System,” in which the vacuum impeller (or “fan”) itself does not encounter dirt, because dirt is filtered from the air before the air reaches the impeller. An inlet for the hose is typically located on the side of the canister. The vacuum motor draws air and dirt into the canister via the inlet hose. The canister is at highly reduced pressure. Debris falls down in the canister. The canister may or may not be lined with a filter bag, which traps the vacuumed debris. Air goes through the filter or filter bag, then through the vacuum motor unit, and out into the ambient air. If a bypass feature is included, ambient air is used for motor cooling. The motor-cooling air is separate from the dirty air in a good workshop vacuum (such as in vacuum “head” units made by Ametek Corp., which are used in many brands of workshop vacuum units). The vacuum “head” unit is the critically important subassembly of a vacuum cleaner, composed primarily of a motor that drives an impeller. The impeller is enclosed within a carefully shaped impeller housing.
Such “clean impeller” systems often have custom-made filter bags which make emptying the canister neater, quicker, and easier. In this approach, the same canister is used as in the conventional workshop vacuum, with a same side nozzle. A large closed paper bag is deployed within the canister; viewed in laid out manner, the bag is rectangular, with a cardboard “collar” in the bag's middle through which the dirty air enters the bag. The collar hooks over the canister's interior projection of the hose nozzle and the canister is lined with the bag. The customer purchases the particular bag customized to the canister. Disadvantageously however, the user must replace the separately-purchased proprietary filter bags every time the vacuum unit was emptied. Conventional “clean impeller” workshop vacuum systems are relatively simple, cheap and reliable. However, disadvantageously, disposable, inexpensive plastic bag liners seemingly cannot practically be incorporated because 1) the bag must be penetrated with the nozzle which breaks the bag seal; and 2) when the workshop vacuum is turned on, a lightweight, inexpensive disposable plastic bag would collapse due to the vacuum inside the canister. Thus there would be nowhere for the dirt to accumulate inside the plastic bag.
Another category of vacuum cleaners is “Dirty Impeller Vacuum Systems.” Dirt and air are drawn directly into the impeller, and the canister is pressurized by the air-plus-dirt output of the impeller, in contrast to “clean” impeller systems. A vacuum impeller can be designed to deal directly with unfiltered, dirt-laden air by altering its blade and fan geometry, selecting appropriate blade materials, and sometimes also coating blades to prevent dirt from sticking to them. The system then pumps air and dirt together into the canister. Clean air is exhausted from the canister via elaborate filters, which get clogged. If the air filter is a filter bag, put over the top of the canister, the filter bag's pores get clogged. When the time comes to empty the canister, usually the bag needs replacing or cleaning.
Vacuum cleaner systems are used in a variety of applications. One application in which vacuum cleaner systems are used is in security destruction machines. Vacuum systems are used in some, but not all, conventional destruction machines. For example, in many conventional shredders, no vacuum is used and the shredded pieces are simply permitted to fall into a waste receptacle. Some high-security shredders do have vacuums, however.
One type of destruction machine is a “disintegrator” which is a certain category of larger destruction machines. A car-sized disintegrator known as Kobra Cyclone, made by Elcoman (Italy) collects waste in a pressurized plastic bag, which lines a large (100 gallon) canister.
An example of operation of a conventional shredder is use of a canister lined with a bag, with a lid on the canister, with a nozzle attached, and the filter bag clamped on, and deployed above the canister. Such structures are sometimes known as “bag houses” (when used in large industrial applications) and may be in an array. The bags in bag houses are all pressurized. Air and dust enter the bag houses through an entry port. The dust tends to fall into the container below the bags. The air comes out through the bags and gets filtered, while the dust stays below, and inside the canister or Bin. In some devices, the “bag house” is simply the cloth or paper bag itself, suspended above the collection canister or Bin. However, this conventional design suffers from the problem of the filter needing frequent cleaning, which requires stopping normal disintegrator operation to permit filter-cleaning. The finer the dust or dirt being filtered, the larger the filter must be, and the more often it needs cleaning.